The present invention relates to a method of manufacturing a substrate provided with a resist film by coating a resist agent on a substrate to thereby form the resist film on the substrate and manufacture, for example, a photomask.
Hitherto, there has been proposed a method of manufacturing a substrate provided with a resist film by coating onto a substrate a resist agent, which is used for forming a resist film, such as a photoresist, on a substrate, such as a silicon wafer, thereby to manufacture the substrate having the resist film. Also, a coating apparatus (or a coater) has been proposed as an apparatus for coating such a resist agent.
What is called a spin coater is known as a conventional coating apparatus. This spin coater spreads a resist agent on a surface, which is to be coated, by the action of a centrifugal force by rotating this substrate in a horizontal plane at a high speed after liquid resist agent is dropped a central portion of a surface of a horizontally supported substrate, which is to be coated. Thus, the spin coater forms a coating film on the entire surface to be coated.
However, such a spin coater has the problem that a projection made of a resist agent, which is referred to as a “fringe”, is produced in a peripheral edge portion of the substrate. When such a fringe is produced, the thickness of the resist film formed of the coated resist agent becomes uneven. Further, such a fringe is liable to be produced, especially, in a large substrate, such as a substrate of a liquid crystal display apparatus and a photomask substrate for manufacturing a liquid crystal display apparatus, the length of which is equal to or more than, for example, 300 nm.
In recent years, in a liquid crystal display apparatus, and a photomask for manufacturing a liquid crystal display apparatus, the degree of a pattern formed therein is enhanced. Thus, techniques enabled to form a resist film having a uniform thickness on the entire surface of a large substrate are desired. That is, in a case where the resist film has a film thickness distribution, in-plane variation of precision of turn-processing, which is performed by using a resist pattern formed of the resist film as a mask, is caused.
In view of such circumstances, a coating apparatus, which is commonly called a “CAP coater”, as described in a Patent Document 1, has been proposed. In this “CAP coater”, a coating nozzle having a capillary-tube-like gap is preliminarily sunk in a liquid tank in which liquid resist agent is stored. Meanwhile, a substrate is held in a position, in which a surface to be coated is downwardly directed, by a suction table. Subsequently, the coating nozzle is lifted from the resist agent so that the top portion thereof is placed close to the substrate surface to be coated. Then, the liquid resist agent stored in the liquid tank is raised due to a capillary phenomenon caused in the coating nozzle, so that this resist agent contacts the substrate surface, which is to be coated, through the top portion of the coating nozzle. Thus, a coating film is formed on the entire surface, which is to be coated, by causing the coating nozzle to perform a relative scan on the entire surface in a state in which this resist agent contacts the surface to be coated.
More concretely, this coating apparatus has a control portion for adjusting the height positions of the liquid tank and the coating nozzle. This control portion first raises both the liquid tank, in which the resist agent is stored so that the liquid level of the resist agent reaches a predetermined liquid level position, and the coating nozzle, which is completely sunk in this resist agent, and causes both the liquid tank and the coating nozzle to approach the substrate surface, which is to be coated, from below. Subsequently, the control portion stops the rise of the liquid tank to thereby project the top side of the coating nozzle upwardly from the liquid level of the resist agent. At that time, the coating nozzle being completely sunk in the resist agent is projected upwardly from the liquid level of this resist agent. Thus, the capillary gap is filled with the resist agent.
Subsequently, the control portion raises the liquid tank together with the coating nozzle again to thereby cause the resist agent at the top portion of the coating nozzle to contact the substrate surface to be coated. Then, the control portion stops the rise of each of the liquid tank and the coating nozzle. That is, the control portion stops the liquid tank and the coating nozzle in a state in which the resist agent filling up the capillary gap of the coating nozzle is brought into contact with the surface to be coated.
Subsequently, the control portion causes the liquid tank and the coating nozzle to descend to a predetermined “coating height” position in a state in which the resist agent contacts the substrate surface to be coated at the top portion of the coating nozzle. In this state, the control portion moves the substrate along the surface direction and causes the top portion of the coating nozzle to scan the entire surface to be coated, thereby to form a resist agent coating film over the entire surface to be coated.
According to the manufacturing method using such a coating apparatus, a resist film having a uniform thickness can be formed over the entire surface of the substrate without producing a fringe on the peripheral edge portion of the substrate.
[Patent Document 1]
JP-A-2001-62370.
Meanwhile, even when the aforementioned coating apparatus commonly called “CAP coater” is used, the uniformity of the thickness of the resist film is sometimes insufficient in a case where the high precision of the pattern formed on the substrate is required.
However, hitherto, it has not been studied whether or not a coating film having a small film thickness distribution rate (to be described later) can be formed and the uniformity of the thickness of the resist film can be enhanced in a case where the resist agent is applied by using such a coating apparatus.